Why does my rig pose change when i render?
Look for keyframe registrations.  If a pose has been keyframed, rendering will set it to the appropriate, keyframed pose.

Following the render, hit &#9096; Ctrl+z to return to your unregistered, unrendered pose, then try advancing a frame (with mouse over the timeline, hit right arrow.)  Does the pose change?  Then you have registered keyframes.  Register your new pose before rendering, or delete existing keyframes.